The main purpose of this study was to produce and test the reliability of predictive models of cetacean distributions off the west coast of Scotland. Passive acoustic and visual surveys were carried out from platforms of opportunity between 2003 and 2005. Acoustic identifications were made primarily of harbour porpoises (Phocoena phocoena), delphinids, and sperm whales (Physeter macrocephalus). Generalised Additive Models (GAMs) were used to relate species’ distributions to a range of environmental variables over a range of temporal and spatial scales. Predictive models of delphinid distributions showed both inter-annual and inter-month variations. Combining all data for all months and years resulted in a model that combined the environmental influences from each monthly and yearly model. Overall, delphinids were found to associate with the deep (> 400m) warm water (10.5°C-12.5°C), and in areas of deep thermocline. Relationships between sperm whales and environmental variables were consistent over changes in grain size (9 km or 18 km), but not between areas. Although sperm whales were distributed in deep water characterised by weak thermoclines and strong haloclines in the most northerly area (Faroe-Shetland Channel), they were found in deep productive areas with cold surface temperature in the more southerly waters (Rockall Trough). Within the southern Inner Hebrides, high use areas for harbour porpoises were consistently predicted over time (in years) and with differing survey techniques (acoustic versus visual), but not over space (southern Inner Hebrides versus whole of the Inner Hebrides). Harbour porpoises were mainly distributed in areas with low tidal currents and with higher detection rates during spring tides. The use of prey as a predictor variable within models of delphinid distribution shows some promise: there were correlations between delphinid and herring (Clupea harengus) in shelf-waters in 2005 but not in 2004. These models can be used in mitigating acoustic threats to cetaceans in predicted high use areas off the west coast of Scotland.

Sperm whales (Physeter macrocephalus) are nomadic species typically studied across broad (>100km) spatial scales. In this study, I model fine-scale (or submesocale) habitat preferences, determine how organization into distinctive units of associating female and juveniles influences habitat use, and describe how movements change across the 24-hour cycle. This study concerns a well-studied population of sperm whales off Dominica in the Eastern Caribbean. Statistical models suggest that overall habitat use is rather homogenous, and social behaviour is best predicted by the presence of mature males. Variation among social units in the amount of time spent, and space occupied, within the study area indicates habitat preferences at the level of the social unit. Finally, movements are influenced by the diurnal cycle, as whales tend to move from inshore to offshore at dusk. This study betters our understanding of sperm whale habitat decisions over fine-scales, and has implication for conservation and management strategies.

De nombreux prédateurs marins se nourrissent directement des prises des pêcheurs. Ces interactions, définies comme de la déprédation, engendrent des conséquences socio-économiques considérables pour les pêcheurs ainsi que des implications de conservation pour la faune sauvage. D’un côté, la déprédation endommage le matériel et augmente l’effort de pêche pour atteindre les quotas. D’un autre côté, la déprédation augmente le risque de mortalité des prédateurs marins (prise accidentelle ou rétorsion létale par les pécheurs). La pêcherie à la palangre est la plus impactée par la déprédation, principalement par les odontocètes, ce qui incite à trouver des solutions. La majorité des études se concentrant sur la déprédation s’est principalement basée sur des observations en surface, de ce fait la manière dont les prédateurs retirent les poissons sur les lignes reste confuse. Par ailleurs, l’impact de la déprédation sur le comportement des pêcheurs ainsi que les facteurs expliquant leur détectabilité n’ont reçu que peu d’intérêt. L’objectif de cette thèse est donc d’étudier ces problématiques par un suivi acoustique, une utilisation de balises et une approche en écologie comportementale humaine, en se concentrant sur la pêcherie palangrière française ciblant la légine australe (Dissostichus eleginoides) impactée par la déprédation des orques (Orcinus orca) et des cachalots (Physeter macrocephalus). Les capitaines ont été décrits comme recherchant leur ressource selon la théorie de « l’optimal foraging », mais avec des perceptions de la compétition et du succès de pêche qui divergent. Certains capitaines seraient ainsi plus enclins à remonter les palangres au plus proche et à rester sur une zone, même en présence de compétition, augmentant alors le risque d’interaction. L’acoustique des navires a révélé que certaines manoeuvres (marche arrière par exemple) propagent différemment sous l’eau. La manière dont les capitaines manoeuvrent leur palangrier influencerait ainsi leur détectabilité et donc leur risque d’interaction avec les prédateurs. D’autre part, l’utilisation de capteurs sur les palangres et les animaux a révélé que les orques et les cachalots sont capables de déprédater sur les palangres posées sur le fond marin. Ces observations laissent à penser que les odontocètes sont en mesure de localiser l’activité de pêche bien avant la remontée de la ligne, ce qui pourrait être expliqué par une signature acoustique spécifique du déploiement de la ligne. L’ensemble des résultats de cette thèse suggère que la déprédation sur les palangres démersales est très probablement sous-estimée. Cette thèse apporte également des éléments importants pour la lutte contre la déprédation, en montrant la nécessité de protéger les palangres dans l’intégralité du processus de pêche. / Many marine predator species feed on fish caught by fishers directly from the fishing gear. Known as depredation this interaction issue has substantial socio-economic consequences for fishermen and conservation implications for the wildlife. Costs for fishers include damages to the fishing gear and increased fishing effort to complete quotas. For marine predators, depredation increases risks of mortality (lethal retaliation from fishers or bycatch on the gear). Longline fisheries are the most impacted worldwide, primarily by odontocetes (toothed whales) depredation, urging the need for mitigation solutions to be developed. Most of studies assessing depredation have primarily relied on surface observation data, thus the way odontocetes interact with longlines underwater remains unclear. Besides, the way fishermen respond to depredation during fishing operations, or can influence their detectability to odontocetes, have been poorly investigated. This thesis therefore aimed at investigating these aspects through a passive acoustic monitoring, bio-logging and human ecology approaches, focusing on the French Patagonian toothfish (Dissostichus eleginoides) longline fisheries impacted by killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus). Firstly, this thesis reveals that captains behave as optimal foragers but with different personal perception of competition and fishing fulfilment. Some captains would thus be more likely to stay within a patch or to haul closest longline even in presence of competition, suggesting these captains would show higher interaction rates. Additionally, the propagation of vessels’ acoustics varied depending on the type of manoeuvre (e.g. going backward vs. forward). The way captains use their vessels to navigate may therefore influence their detectability and so their depredation level. Secondly, loggers deployed on both the longlines (accelerometers) and odontocetes (GPS-TDR) revealed that killer whales and sperm whales are able to depredate on longlines while soaking on the seafloor. These observations suggest, therefore, that odontocetes can localise fishing activity before the hauling, which could be partially explained by specific acoustic signatures recorded during the setting process. Altogether, the results of the thesis suggest that depredation rates on demersal longlines are most likely underestimated. The thesis also brings some important insights for mitigation measures, suggesting that countermeasures should start from setting to hauling.

Within-population behavioural variation can greatly affect the ecology of a species and the outcome of evolutionary processes. This study aimed to determine how variable sperm whale social and vocal behaviour is between both individuals and their social units. The population of whales off Dominica is small and isolated from communities in neighbouring waters. Female and immature whales live together in social units containing about 7 animals. I analysed their social relationships and their ‘coda’ communication signals using an unparalleled dataset of social and vocal interactions at the level of the individual. Within units, calves were significant nodes in their social unit’s network, and thus I provide quantitative support for the hypothesis that communal calf care acts as the primary evolutionary driver for group formation in this species. Social relationships within and between units were diverse, while the spatial spread of individuals within units and their travel speeds were similar among all of the units. I identified long-term patterns of association between units consistent over decadal time scales. Social units had characteristic vocal repertoires, but all were dominated by the ‘1+1+3’ and ‘5R’ coda types. Differences between units resulted from some units using specific 4-click coda types. Units and individuals used different accents on their ‘5R’ codas, but the ‘1+1+3’ coda was stereotyped across all individuals and units studied. The repertoires of different units were as similar as units within vocal clans in the Pacific. My results support the hypothesis that the ‘5R’ coda may function in individual identification. The stability of the ‘1+1+3’ coda may be the result of selection for a marker of clan membership. Individual repertoires differed consistently across years; and contrary to an existing hypothesis, new mothers did not vary their repertoire to be more distinct after giving birth. However, calves did use a class-specific ‘3+1’ coda. In summary, sperm whale social and vocal behaviour vary between individuals and among units. Variation in the social and vocal behaviour of female sperm whales results from a trade-off between individuality and conformity within units and clans.

The subpopulation of sperm whales (Physeter macrocephalus) in the Mediterranean Sea is presently list as “Endangered”. This study is an attempt to provide detailed data on sperm whale Bachelor Groups surrounding Ischia, Italy in the Tyrrhenian Sea (Mediterranean Sea). 24 hours, 38 minutes, and 38 seconds of sperm whale Bachelor Group acoustic data was analyzed in order to describe acoustic repertoire, classify behavioral associations to acoustic types, and identify habitat-use. The data showed that the acoustic repertoire of sperm whale Bachelor Groups is dominated by Usual Clicks. Additionally, a click type that maintains an inter-click interval (ICI) in between Usual Clicks and Creaks was identified during acoustic analysis and named “Transition Clicks”. Acoustic events were categorized into Single Code and Combination Code events; representing situations where one acoustic code was heard versus situations where two or more different acoustic codes were heard simultaneously. Analysis revealed that Single Code events represented 71.25% of the sperm whale Bachelor Group acoustic repertoire. The Usual Click/ Transition Click combination represented 73.74% of Combination Code events. A significant difference was shown between time spent in Single Code versus time spent in Combination Code for Usual Clicks and for Squeals. Acoustic repertoire data revealed the possibility for a strong collaborative acoustic structure and a speculated strategy for evolutionary success among sperm whale Bachelor Groups in Ischia, Italy. Additionally, the study showed that sperm whale Bachelor Groups spend 77.87% of the analyzed time engaged in orientation/searching/foraging behavior and 1.09% engaged in socializing behaviors. Event maps revealed a ‘hotspot’ of sperm whale Bachelor Group activity in the waters to the northwest of Ischia, Italy, within the submarine Canyon of Cuma, and outside of the boundaries for the Regno di Nettuno Marine Protected Area (MPA). It is recommended that the results of this study be utilized in extending the Regno di Nettuno MPA to include the ‘hotspot’, and possible critical area, for sperm whale Bachelor Groups. The results of this study and published literature of the sperm whales in this area could be utilized to create population-specific management strategies for more effective measures in ending population decrease and preserving the species. Further research should be carried out to analyze in detail the role of Transition Clicks in sperm whale acoustics and the possibility of a collaborative acoustic structure that has yet to be displayed in any other sperm whale population worldwide.

Behavioural responses can reveal important fitness trade-offs and ecological traps in evolutionarily novel contexts created by anthropogenic stimuli, and are of increasing conservation concern due to possible links to population-level impacts. This thesis illustrates the use of proxies for energy acquisition and expenditure within multivariate and state-based modelling approaches to quantify the relative time and energetic costs of behavioural disturbance for a deep-diving marine mammal (Physeter macrocephalus) in foraging grounds in Kaikoura Canyon (New Zealand) and near Lofoten Islands (Norway). A conceptual framework is first developed to identify and explore links between individual motivation, condition and external constraints to behavioural disturbance [Chapter 1]. The following chapters then use data from behavioural response studies (BRS) to: 1) derive biologically relevant metrics of behaviour [all chapters], 2) investigate effects of boat-based focal follows and tagging procedures [Chapters 2-3], and 3) relate responses to specific disturbance stimuli (distance, approach, noise) from whale-watching [Chapter 2], naval sonar and playback of presumed natural predator (killer whale Orcinus orca) sounds [Chapter 4]. A novel hidden state model was developed to estimate behavioural budgets of tagged sperm whales from multiple streams of biologging (DTAG) data [Chapter 3]. Sperm whales traded off time spent at foraging depths in a non-foraging and non-resting state in response to both tag boat presence, 1-2 kHz naval sonar (SPL 131-165 rms re 1μPa) and mammal-eating killer whale sound playbacks, indicating that parallel non-lethal costs were incurred in both anthropogenic disturbance and presumed antipredatory contexts. While behavioural responses were highly variable by individual, biologically informed state-based models appeared effective to control for variability in energy proxies across different functional contexts. These results and Chapter 5 “linking buzzes to prey” demonstrate that behavioural context is a signal that can aid understanding of how individual non-lethal disturbance responses can impact fitness.